Calcium-acidic phospholipid-phosphate complexes have been associated with the initiation of in vitro and in vivo mineralization. The concentration of such ccmplexes has been found to be maximum in the hypertrophic zone of the epiphyseal growth plate and in the early stages of healing fracture callus. Pathological calcifications (submandibular salivary stones, calcified aortas, and chondrocalcinosis specimens) and abnormally calcified specimens (rachitic bone, tidemark zone of articular cartilage) are now being examined to determine the distribution of such complexed lipids. The presence of elevated levels of such complexed acidic phospholipids in disease bone (osteoarthritis, osteonecrosis) is being compared to the low levels in non-diseased (control) bone. At the same time, the factors involved in controlling the formation of the complexed acidic phospholipids, and those involved in promoting or inhibiting proliferation of hydroxyapatite by complexed phospholipids are being evaluated. These factors include the Ca:PO4 ratio, the concentration of Ca, Ph, and the presence of proteoglycans, and phospholipases. Structural studies of the calcium salts of phosphatidyl serine and phosphatidyl inositol, and calcium-phosphatidyl serine-phosphate, and calcium phosphatidyl inositol-phosphate are being carried out using P31NMR, laser raman spectroscopy, infrared spectroscopy and x-ray diffraction.